PowerPoint Presentation - Deamination

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Unit 3AHuman Form Function
Cells, metabolism regulation Regulation of
fluid composition
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Study Guide

• Read
• Human Prespectives 3A/3B Chapter 8
• Complete
• RQ 10-14
• AYK 5-12

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Structure of the kidney
Proximal convolute tubule
Distal convolute tubule
Capsule
Cortex
Renal corpuscle
Medulla
Pyramid
Renal artery
Collecting duct
Renal vein
Loop of Henle
Pelvis of ureter
Peritubular capillaries
Ureter
LS of KIDNEY
A NEPHRON
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Kidneys functions

• Fluid balance
• Salt balance
• Removal of wastes (especially urea)
• pH balance

Interdependent
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Fluid balance

• The kidneys play an important role in the
  homeostatic regulation of body fluids (both the
  amount and the composition).
• If we become dehydrated the kidneys can increase
  the reabsorption of water from the filtrate,
  whilst also increasing the secretion of salt. If
  our tissue fluids are too dilute the opposite
  occurs.

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Water reabsorption

• 60-70 of water reabsorption occurs in the
  proximal convolute tubule.
• The remaining 30-40 is selectively reabsorbed
  in the loop of Henle, distal convolute tubule and
  collecting duct, depending on our state of
  dehydration.
• How much water is reabsorbed at both stages
  depends on our state of dehydration i.e. less
  water is reabsorbed if our tissue fluid is
  dilute more if we are dehydrated.

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Urine formation

• There are three stages in urine formation
• Filtration (in the renal corpuscle)
• Selective reabsorption (mainly in the proximal
  convolute tubule some water and salts are
  reabsorbed in the loop of Henle and the distal
  convolute tubule)
• Tubular secretion (in the proximal convolute
  tubule and the distal convolute tubule)

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EM of a glomerulus
D Gregory D Marshall, Wellcome Images
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Filtration
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Section showing Bowman's capsule, glomerulus and
tubules
Bowman's capsule
Glomerulus
Tubule
Wellcome Photo Library
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Selective reabsorption
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Tubular secretion
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Selective water reabsorption

• The second stage of water reabsorption is
  important if we become dehydrated.
• It can be divided into two phases (though both
  are interdependent).
• The first phase involves the reabsorption of salt
  under the influence of the hormone aldosterone.
• 2. The second phase involves the reabsorption of
  water under the influence of the antidiuretic
  hormone (ADH).

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Reabsorption of salt under the influence of
aldosterone

• Stimulus
• Decreased blood volume ? reduced blood
  pressure
• Receptor
• Baroreceptors in Renal artery

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• Transmission
• Several chemical messengers ending with release
  of aldosterone from the adrenal cortex
• Effector
• Sodium pumps in DCT and loop of Henle
• Response
• Sodium reabsorbed increasing ion concentration
  in interstitial fluid(creates osmotic gradient)

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Low Na concentration In filtrate
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Negative feedback loop
Decreased blood volume ? reduced blood pressure
Baroreceptors in Renal artery
Stimulus
Receptor
End-product is aldosterone from adrenal cortex
Creates osmotic gradient
Control centre
Feedback
Response
Effector
Sodium pumps in DCT and loop of Henle
Sodium reabsorbed
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Reabsorption of water under the influence of
antidiuretic hormone

• Stimulus
• Decreased blood volume ? reduced blood
  pressure ? increased osmotic pressure
• ReceptorOsmoreceptors in hypothalamus ?
  (activates thirst reflex)

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• Transmission
• nerve signal to posterior pituitary gland ADH
  released into bloodstream
• Effector
• DCT and collecting duct
• Response
• Increases permeability of above
  structures water (approx 10) reabsorbed

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ADH increases permeability of tubule
Relatively dilute filtrate
Water leaves the filtrate by osmosis
Relatively concentrated tissue fluid
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Negative feedback loop
Decreased blood volume ? reduced blood pressure
? increased osmotic pressure
Osmoreceptors in hypothalamus
Stimulus
Receptor
Osmotic pressure maintained or reduced
ADH from posterior pituitary gland
Control centre
Thirst reflex
Feedback
Drink
Waterreabsorbed
Response
Effector
DCT and collecting duct
Increases permeability of DCT and collecting duct
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Deamination

• Definition - The stripping of nitrogen from amino
  acid and nitrogen bases (RNA)
• Deamination occurs in the liver
• Amino acid ? ammonia organic compounds for
  respiration
• Ammonia (very toxic) CO2 ? urea (H2NCONH2)

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Nitrogen Wastes